Stored program controlled communication switching systems comprise some form of intelligence which controls switching functions in response to a program stored in memory. Historically, such systems included a single processing entity for the control of the entire system. As technology and system design evolved, it was found desirable to separate certain routine functions from the main processing entity to save its processing time for more complex system functions and decisions. Today, systems are being designed which also separate some of the more complex system functions and decisions into several intelligent processors. Throughout the evolution of switching system control strategies, changes have occurred in the way the various processing entities intercommunicate. Some systems have provided a separate controller bus structure to be used for all communications among the processors. Other systems have utilized the communication paths of the switching network to provide communication paths between the distributed system processors and a central controller which interprets control information and directs the overall operation of the switching system.
The systems which communicate control information using the switching network communication paths generally preempt permanently a small number of recurring time separated channels from conveying speech representations or data and use them to convey control information. A large number of such channels cannot be permanently preempted without affecting substantially the capacity of the switching system. The small number of permanently assigned channels provide sufficient information transfer capacity for the routine operation of the switching system. However, when large amounts of information are to be transmitted, the capacity may prove insufficient. For example, when a large program needs to be written into the memory of a distributed processor, e.g., a program update, too much time may elapse before the write operation is completed. Further, utilizing all of the control information conveying channels may preclude the distributed processor from performing its function of controlling a part of the switching system.
It is an object of the present invention to provide a high capacity control information communication system for conveying large amounts of data utilizing the communication paths of the switching network between a central controller and a distributed processor the use of which does not terminate the distributed processor's ability to control the switching system.